The alien flora of the Cape of Good Hope Nature Reserve

An annotated species list of the alien vascular plant flora of the Cape of Good Hope Nature Reserve is presented. The flora comprises five gymnosperm and 68 angiosperm species that are definitely alien to the reserve and four angiosperm species that are possibly alien. The life-form distribution of the alien flora is shown to be significantly different from that of the indigenous flora; trees, shrubs and annual herbs are more important in the alien flora, and dwarf shrubs and perennial herbs are much less important. Biotic factors are suggested as being important in determining the success of alien invasions, in particular grazing by ungulates. The invasion rate is currently about one new species per year. By ceasing to introduce tree species and by restricting human disturbance, the rate of invasion of new species could be reduced

The history and effects of alien plant control in the Cape of Good Hope Nature Reserve, 1941–1987

Concern about the invasion of this reserve by alien trees and shrubs, principally Acacia cyclops, A. saligna, A. longifolia, Eucalyptus lehmannii and Pinus pinaster, was first expressed in 1941, 2years after its proclamation. Control operations were started by 1943 and were almost totally ineffective for at least the first 35years; no systematic control strategy was implemented, follow-up control work was inadequate to prevent reestablishment of felled thickets and the supervision of control teams was deficient. Linkage of control operations to firewood production was a significant factor in this failure. In 1974 a 10-year control strategy was drawn up and in the late 1970’s began to be effectively implemented. Surveys of 40 plots in the centre of the reserve in 1966, 1976–80 and 1986 showed increasing densities of species other than the easily controlled P. pinaster up to 1976–80. Since then almost all individuals>1,8m in height have been eliminated and indications from smaller height classes are that seed banks are being depleted. Explanations are advanced for the successes and failures experienced during the 47years of control. Some of the side-effects of these invasions and their control are discussed. One conclusion is that this reserve requires a qualified ecologist on its staff

Regeneration of a Natal coastal dune forest after fire

The composition of alcoastal dune forest in the MIalazi Nature Reserve, Natal was studied three years after a fire and compared with adjacent unburnt forest. The two communities had similar plant densities but there was a marked decrease in biomass and diversity in the burnt community. Measured as density, basal area or canopy volume, Trema orientalis contributed over 70% of the regenerating burnt forest. Saplings of some forest trees were-present but those of Mimusops caffra, the dominant tree of the unburnt community, were absent from the burnt area. S. A fr. J. Bot. 1985, 51 : 453 — 459Die samestelling van ‘n kusduinwoud te Mlalazi-natuurreservaat, Natal is drie jaar na ‘n brand bestudeer en met aangrensende ongebrande woud vergelyk. Die twee gemeenskappe se plantdigtheid was dieselfde, maar daar was ‘n merkbare afname in biomassa en verskeidenheid in die gebrande gemeenskap. Gemeet as digtheid, basale oppervlakte of blaredak-volume het Trema oriental is meer as 70% van die regenererende gebrande woud bygedra. Lote van sommige woudbome was aanwesig maar die van Mimusops caffra, die dominante boom van die ongebrande gemeenskap, was afwesig in die gebrande gebied. S.-Afr. Tyciskr. Plantk. 1985, 51: 453 – 45

Range expansion of the hadeda ibis Bostrychia hagedash in southern Africa

The southern African range of the habeda ibis Bostrychia hagedash has expanded from 530 900 km 2 in 1910 to 1 323 300 km2 in 1985. Major range expansions have occurred in the fynbos biome of the south-western Cape, the Karoo, the grasslands of the eastern Cape, the Orange Free State and the Transvaal highveld. Smaller expansions are documented for Lesotho, eastern Zimbabwe, central Mozambique and westwards along the Zambezi, Okavango, Limpopo and Orange rivers. The reasons for this expansion were investigated. Important factors include reduction in human persecution following the introduction of legislation in the period 1934 to 1941 and an increase of alien trees in formerly treeless areas. The increases in artificial impoundments and areas under irrigation are thought to have played a smaller role

Pattern and process in a semi-arid grassveld in Rhodesia.

The study was conducted on the grass component of Redsoil veld at four sites in the vicinity of Bulawayo, situated in the medium rainfall (400 to 700 mm) zone of Rhodesia. A pattern in which the veld consists of a mosaic of scattered "degraded patches" of varying shapes and sizes set in a matrix of "sound veld" is demonstrated. The distribution of selected grass species within this mosaic is shown. Rainfall induced changes in yield relationships and species distributions within this pattern were followed over four growing seasons. The pattern is shown to be related to variations in the infiltration capacity of the surface soils, and causative mechanisms are postulated.Keywords: bulawayo; grass; grasses; infiltration; rainfall; redsoil; relationships; rhodesia; semi-arid grassveld; soils; species distribution; variation; veld; yield; zimbabw

A List of Alien Plants in the Kruger National Park

The alien vascular plant flora of the Kruger National Park is listed. Annotations cover the invasive status, modes of introduction and dispersal, dates of first recording, ecological impacts and control status of each species. The list comprises 156 species of which 113 are considered invasive within the park. Most of the species have been accidentally introduced to the park. The ecological impacts of 27 species (of which 11 are trees and shrubs) were rated as moderate or high. By 1985 only 10 species are thought to have been eradicated from the park. Most of the invasive species are herbaceous weeds of man-disturbed sites and the eradication of these is generally considered impossible. Most of the important species are dispersed by water and animals. The significance of limiting reinvasion of the park down the rivers flowing into the park, is stressed